Field of the Invention
This invention relates to concrete and, more particularly, to novel systems and methods for formulation of concrete mixtures to improve mechanical and processing properties and characteristics.
Background Art
Concrete is a common construction material. It is used for footings and foundations routinely. It is sometimes used for walls of buildings or other walls for other architectural purposes. It is sometimes used for floors and ceilings of buildings. It has been formulated over many years to include aggregate, cement, and water. It is typical in construction that higher ratios of water to cement will compromise the compressive strength of concrete. Concrete has a comparatively little tensile strength.
Meanwhile, reducing the ratio of water to cement creates challenges in the workability of concrete. Typically, the ratio of water to cement influences a property called slump. Slump characterizes the tendency of concrete to flow down due to fluid in it rather than to stack up due to aggregate in it. Inasmuch as concrete is largely solid material, commonly called aggregate and constituted by coarse aggregate such as rock, gravel, or both, and fine aggregate constituted by some type of sand, the solid materials may tend to stack if the cement is comparatively thick or stiff. With more water, the cement fluid or “paste” formed by the wetted cement powder and added water tends to lubricate and separate the aggregate such that it will flow down to a greater extent.
Low ratios of water to cement tend to produce stronger concrete (greater compressive stress before failure limits), whereas greater ratios of water to cement tend to delay setting up of the concrete, and thereby provide improved ability to work the concrete, form it, surface treat it, finish it, and so forth. Also, more working time and better flow improves the reduction of voids, the compacting or vibrating of the aggregate into place, the filling in by the cementitious fluid of cement and water among all the interstices, and so forth.
Concrete has various phenomena acting during its cure process. Curing is a chemical process whereby the cementitious fluid becomes a solid by the chemical reaction of water with the cement. Curing involves both reaction of molecules of the cement with the water and with each other to form bonds. It also involves a drying process whereby any excess water may be evaporated away from the concrete.
During cure of concrete, the presence or absence of water may affect the curing, cracking, strength, and so forth. For example, external surfaces may tend to dry too quickly. This causes shrinkage and small cracks. Meanwhile, the internal portion of a concrete structure may take more time, but may have insufficient water to complete the chemical reactions that are available with the molecules of the cement material.
Thus, two types of concrete curing are common. One is to provide a water layer over the concrete to maintain hydration at the surface and prevent drying during cure. Another is to rely on sufficient internal water, sometimes a comparatively excess amount of mixed in water, while also covering the concrete or sealing it against evaporation. Thus, one method is referred to as a wet cured concrete in which the surface is maintained and moist. The other is called internal cure
It would be an advance in the art to provide a mechanism that could improve workability of concrete, without compromising its ultimate strength. It would also be an advance in the art to provide water during internal curing. It would also be an advance to do so without leaving voids of a size that creates stress concentrations and initiates fractures. It would also be an advance to better seal against perviousness, and reduce shrinkage and its associated stress, strain, and cracking in concrete.